Hydraulic and industrial functional fluids are required to exhibit a number of performance characteristics and this is usually achieved by blending a base oil (stock) with a multi functional additive package. Conventional packages are designed for use in Group I base stocks. However, the number of refiners producing Group II and Group III base stocks has increased recently, and the use of these base stocks has posed a number of challenges to formulators not encountered with Group I base stocks.
Group II and III base stocks are produced by hydro processing and this reduces the aromatics content of the base stock resulting in differences in base stock solvency. Differences exist between different Group base stocks and between base stocks within the same Group. The reduced aromatics content of the base stock means that certain surface active components used in conventional hydraulic and industrial additive packages, such as demulsifiers, that function well when used in Group I base stocks do not always have sufficient solubility in all Group II and all Group III base stocks. For example, conventional demulsifiers such as copolymers of ethylene oxide and propylene oxide provide satisfactory demulse performance and are fully soluble in Group I base oils but, at useful concentrations, tend not to be fully soluble in Group II and Group III base oils. Poor demulsifier solubility results in formulated blends which are dull. Although these may be merchantable, they will also exhibit derated performance due to the presence of precipitates. The latter are particularly troublesome as precipitates can lead to clogging or blocking of the very fine filters which are typically used in, for example hydraulic apparatus, to maintain fluid cleanliness. Further, if hydraulic fluids become contaminated with such precipitates, power transmission capability can be lost and the possibility of equipment damage arises.
In accordance with the present invention a specific type of compound has been identified which provides good demulse performance and which exhibits superior solubility in the range of base oils formulators would like to use, including Group II and Group III base oils.